Dual rotation propeller



De. 12, 1950 e. w. BRADY ETAL DUAL ROTATION PROPELLER 12 Sheets-Sheet 1 Filed Jan. 19, 1944 INVENTORl EGevnszWBmor. f CHAzLLSWCMLM ATTURNEY.

1950 G. w. BRADY EI'AL 2,533,346

DUAL ROTATION PROPELLER Filed Jan. 19, 1944 12 Sheets-Sheet 2 V IN VE N TORS. GEO EGE' WEE/J 0 r.

762 C/m ELEJ WCH/L LSON.

Dec. 12, 1950 G. w. BRADY ETAL 2,533,346

mm. ROTATION momma Filed Jan. 19, 1944 12 Sheets-Sheet a.

INVENTOES GEORGE .BRADH 7 CHARLEsWCg/LLsoA/ ATTO NE)? Dec. 12, 1950 G. w. BRADY mL 2,533,346

DUAL ROTATION PROPELLER Filed Jan. 19, 1944 12 Sheets-Sheet 5 l/Vl/EN T ORJ. 287 270 w 276 GEOEG'E WBEADV.

By CA 1. Es WCH/z LSON.

'z' ATTRNEY Dec. 12, 1950 G. w. BRADY ETAL DUAL ROTATION PROPELLER 12 Sheets-Sheet 6 Filed Jan. 19, 1944 [NVE/VTUFJ. GEOIEG E WBQA 0 Y. CHA 1. WCH/L LSOM Dec. 12, 1950 G. w. BRADY EIAL DUAL ROTATION PROPELLER 12 Sheets-Sheet '7 Filed Jan. 19, 1944 INVENTORS. GEORGE WEE/10X C' mass WCH/LLSOM A TTORNEY- Dec. 12, 1950 G. w. BRADY ETAL DUAL ROTATION PROPELLER 12 Sheets-Sheet 8 Filed Jan. 19, 1944 INVENTORJ. CEO RGE WBenor; By CHARLES WCl-(IL 1.50M

ATTS YNEY.

Dc. 12, 1950 s. w. BRADY ETAL 4 DUAL ROTATION PROPELLER Filed Jan. 19, 1944 12 Sheets-Sheet 9.

Fflyfl INVENTORS. GEORGE WERADK BY CHRL ES WCH/L LSO/M D 1950 G. w. BRADY ETAL 2,533,346

DUAL ROTATION PROPELLER Filed Jan. 19, 1944 l2 Sheets-Sheet 10 .7 9 K as IN V EN TOR-'5. GEO/ea: W524 0). BYCHAEL ES WCH L LSO/V.

ATTO

Dec. 12, 1950 a. w. BRADY EIAL DUAL ROTATION PROPELLER 12 Sheets-Sheet 11 Filed Jan. 19, 1944 INVENTORS. C5020: WBPADK BYCHAELES WCH/LLSO/V.

ATTORN a. w. BRADY arm.

mm. ROTATION momma Dec. 12, 1950 12 Sheets-Sheet 12 Filed Jan. 19, 1944 lII/Il/l/ll/llll INVENTORS. G'soea': WEB/ID)- CH RLES WCHILLSOM' ATTORNEY.

WNN

Patented Dec. 12, 1950 DUAL ROTATION PROPELLER George W. Brady, Upper Montclair, and Charles W. Chillson, Caldwell, N. J., assignors to Curtiss-Wright Corporation, a corporation of Delaware Application January 19, 1944, Serial No. 519,066

13 Claims.

This invention relates primarily to dual rotation propellers or those consisting of two sets of propeller blades carried in respective hubs caxially mounted one behind the other and arranged to rotate in opposite directions, and more particularly to the combination of such propellers with pitch-changing or varying mechanisms therefor, whereby the pitch of both sets of propeller blades may be altered as desired.

For a number of reasons well-known to those skilled in the art, dual rotation propellers of the type mentioned above, which consist of two sets of counter-rotational blades, have many advantages over the conventional propeller employing but a single set of blades. Also, for well-known reasons it is highly desirable and in most cases a necessity that the pitch of the propeller blades, whether the propeller is of the dual rotational or the conventional single type, be capable of being varied. Varying the pitch of propeller blades enables the same, in combination with the engine employed to rotate them, to operate more eificiently under greatly varying conditions. For example, when an airplane is taking off, the blades should be in a low pitch position in order that the engine will not be overloaded, whereas at high altitudes the blades should have a relatively high pitch to enable the same to absorb the power of the engine without overspeeding. It is a relatively simple matter to construct pitch-changing mechanisms for single rotation propellers, and many such mechanisms have been used heretofore. However, it will be obvious that to vary the pitch of the dual rotation propeller having two sets of counter-rotational blades requires a pitch-changing mechanism quite different from those employed with single propellers, since in such mechanisms the problems encountered are complicated by reason of the fact that the two sets of blades rotate in opposite directions.

Accordingly, it is one of the primary objects of the present invention to provide a novel and improved dual rotation propeller and pitch varying or changing mechanism therefor wherein the varying of the pitch of the propeller blades is electrically controlled.

In connection with the above, it is a more specific object of the present invention to provide such a dual rotation propeller pitch-changing mechanism wherein a single electric motor is employed in such a manner that the pitch of both sets of propeller blades is altered or varied simultaneously by power furnished from said motor.

Another object of this invention is to provide a dual rotation propeller and a pitch-changing mechanism therefor with a separate gear system for each set of propeller blades which are interconnected through a difierential gearing system whereby the pitch-changing movement of one set of blades is coordinated with that of the other.

Still another object of this invention is to provide a dual rotation propeller pitch-changing mechanism of the above type which includes an arrangement for holding the pitch of both sets of blades in the positions to which they are set by said pitch-changing mechanism during nonoperating periods of said mechanism.

In connection with the above, it is a more specific object of this invention to provide electromagnetically operated means or braking device for holding the blades of both propellers in fixed pitch positions during the non-operating periods of the pitch-changing mechanism.

Still another object of this invention is to provide a dual rotation propeller pitch-changing mechanism having an interconnected gearing system and employing flexible driving means therein whereby limited transverse movement of one propeller relative to the other is permitted.

Still another object of this invention resides in the provision of means for lubricating the various component elements of a propeller of the above type.

The above and further objects will be more apparent in the following detailed description of the present invention wherein reference is made to the accompanying drawings illustrating the preferred embodiment thereof, and wherein:

Figure 1 is a vertical sectional view, partly in elevation, taken substantially through the longitudinal center axis of a dual rotation propeller with pitch-changing mechanism therefor constructed in accordance with the present invention;

Figs. 2, 3, 4 and 5 are enlarged sectional views of various parts of the propeller and pitch-changing mechanism shown in Fig. 1;

Fig. 6 is an enlarged transverse sectional view, partly in elevation, taken substantially on the line 66 of Fig. 1;

Figs. 7, 8 and 9 are transverse sectional views, partly in elevation, taken substantially on the lines l'l, 88 and 99, respectively, of Fig. 4 and illustrating the details of one of the inboard speed reduction units;

Figs. 10 and 11 are enlarged transverse sectional views taken substantially on the lines iii-l and Hl I, respectively of Fig. 1;

Fig. 12 is an enlarged transverse sectional view taken substantially on the line I2-l2 of Fig. 3;

Figs. 13 and 14 are enlarged transverse sectional views taken substantially on the lines 13-43 and -14, respectively, of Fig, 1;

Fig. 15 is an elevational view of one of the units of the flexible interconnecting members employed to connect the pitch-changing mechanisms of the two sets of blades;

Fig. 16 is a transverse sectional view taken substantially on the line I 6-l6 of Fig. 15;

Figs. 1'7, 18 and 19 are transverse vertical sectional views taken substantially on the lines I1l'|, l8l8 and I9-|9, respectively, of Fig. 1;

Fig. 20 is a vertical sectional view taken substantially on the line 20-20 of Fig. 5;

Fig. 21 is an enlarged transverse sectional view taken substantially on the line 2l2l of Fig. 1;

Fig. 22 is a horizontal sectional view taken substantially on the line 2222 of Fig. 21;

Fig. 23 is a fragmentary sectional view taken on a plane at a slight angle to the plane of Fig. 3; and

Fig. 24 is a circuit diagram.

In general terms, the present invention consists mainly of a composite or compound propeller having two sets of coaxially mounted propeller blades arranged to rotate in opposite directions and a coordinating gearing system interconnecting the pitch-changing mechanisms of the two propellers whereby the pitch of both sets of blades is varied by power derived from a single source. The two sets of propeller blades are carried by associated hubs mounted one behind the other, and while the hubs preferably rotate at the same speed but in opposite directions, such a condition, as will hereinafter be apparent, is not essential for the proper operation of the complete propeller or the pitch-changing mechanism of the present invention. If desired, one propeller hub may rotate at a speed different from the speed of the other, and there need be no fixed relationship between said speeds.

In the embodiment of the invention about to be described, and as illustrated in the drawings, each of the two coaxially mounted hubs carries a set of three propeller blades. It will be obvious, however, that the invention is in no manner limited to this particular number and arrange ment of propeller blades, since the principles thereof may be employed in conjunction with or incorporated into a composite propeller of two sets of blades, each of which has a larger or smaller number of blades than three, and one set of blades may consist of a different number than that of the other. For example, instead of the arrangement shown in the accompanying drawings, both sets may consist of two or four blades each, or one set may consist of two blades and the other three.

The complete propeller is hereinafter described as consisting of two individual propeller units, the one nearest the engine together with its associated or component elements being referred to as the inboard propeller, while the one farthest from the engine with its component elements is referred to as the outboard propeller. The blades of each individual propeller are mounted or anchored in sockets in their respective hubs in the usual manner by means of a thrust bearing consisting of a plurality of superimposed rings of ball bearings whereby the blades may rotate or turn about their respective longitudinal axes to vary or change the pitch thereof. A gear, which is generally known as a blade gear, is non-rotatably attached to the shank of each blade. All of the blade scars on each hub mesh with a common driving gear, lmown as the power gear, which is carried by the hub and concentrically mounted with respect to the propeller-shaft bore thereof.

In the described embodiment of the invention the inboard power gear is driven directly through associated speed-reducing or torque-amplifying gearing by an electric motor, located between the two propeller units, in the same general manner as in the case of an ordinary single electric propeller, the operation of which is well understood in the art. The electric motor is concentrically mounted on the inboard propeller hub and is of the hollow-armature, reversible type, whereby the blades may be turned in either direction in their sockets to increase or decrease the pitch thereof.

The outboard propeller pitch-changing mechanism is a separate unit, but is similar in principle of operation to that of the inboard propeller. It, also, comprises speed-reducing gearing through which the outboard power gear is driven, but since the outboard propeller is arranged to rotate in an opposite direction to the inboard propeller and the electric motor carried thereby, the outboard gearing cannot be directly connected to said motor, as in the case of the inboard propeller. To meet this condition and to properly coordinate both pitch-changing units and enable a single electric motor to furnish the power for varying the pitch of both sets of blades, a so-called inter-gearing mechanism which operates on the differential principle is employed. The inter-gearing mechanism at all times coordinates the pitch-changing movement of one set of blades with that of the other while permitting relative rotation between the pitch-changing units associated therewith, and the arrangement is such that the pitch of both sets of blades increases or decreases simultaneously at the same rate, or at rates differing one from the other in predetermined ratio, as desired.

During rotation of the two propeller units, the centrifugal forces acting on the blades thereof tend to rotate the blades about their longitudinal axes to their low pitch positions and, to prevent such pitch-changing movements of the blades at times when the pitch-changing electric motor is unenergized, magnetically controlled brakes are employed. The electric circuits to the brakes are so arranged that the brakes are released when the motor is energized, and vice versa.

The above brief and general description of some of the principal elements or units included in the mechanism of the present invention and the arrangement thereof is for the purpose of giving a general outline of the invention, and in view thereof the following detailed description, wherein reference is made to the accompanying drawings, may be more readily understood.

Referring now to the drawings and particularly to Figs. 1, 2 and 3, the reference numeral 3| indicates generally the outboard propeller shaft and reference numeral 32 indicates generally the inboard propeller shaft. The outboard and inboard shafts 3| and 32, respectively, are supported in suitable bearings (not shown), which may be located in the housing of the engine employed to rotate said shafts. The shaft:

are adapted to rotate in opposite directions and are both hollow, with the inboard shaft 32 in the form of a sleeve surrounding the right-hand portion of that part of the outboard shaft shown in the drawings. The inboard shaft 32 has formed thereon external splines 33 adapted to engage cooperating internal splines 34 in the center bore of the inboard propeller hub, indicated generally by reference numeral 36, whereby the hub is secured to the shaft 32 for rotatable movement therewith as a unit. The hub 36 is mounted and centered on the inboard shaft 32 in the usual manner by means of a pair of mounting cones, namely, a rear cone 31 and a front cone 38. The inboard shaft 32 has external threads 39 adjacent its left-hand end adapted to engage internal threads on a so-called inboard shaft nut 4|. When the nut 4| is tightened on the shaft 32, the front cone 38 and the rear cone 31. which abuts a radial flange 40 on the shaft, cooperate with conical surfaces on the interior of the inboard hub 36 to thereby center the same on the shaft 32.

The shaft nut 4| is locked to the inboard shaft 32 by a locking ring 42. The ring 42 has external splines 43 thereon which engage internal splines formed on the left-hand end of the nut 4|. The locking ring 42 is prevented from rotating relative to the inboard shaft 32 by means of inwardly projecting lugs 44 thereon engaging suitable radial slots in the extreme end of the inboard shaft. The locking ring 42 is placed in position by inserting the same in the space formed therefor after the shaft nut 4| is tightened on the inboard shaft, and since the external splines 33 on the ring are relatively close together, the nut can be locked to the shaft in practically any position. The ring 42 is held in place and prevented from axial movement along the shaft 32 by means of a radially expandable snap ring 46 which expands into a suitable interior groove on the inside of the left-hand end of the nut 4|.

With the exception of a relatively small flange 4! formed integrally with the outboard shaft 38 adjacent the end of the inboard shaft, the .1

outside diameter of the outboard shaft is considerably smaller than the inside diameter of the inboard shaft 32 whereby a clearance space represented by the reference numeral 48 is provided between the two shafts substantially throughout the entire length of the inboard shaft. Since the outboard shaft 3| is substantially longer and smaller than the inboard shaft 32, it has more of a tendency to whip or flex than the inboard shaft, and in order to keep the flexing of the outboard shaft 3| at a minimum, an intershaft bearing of the ball type, indicated in general by reference numeral 49, is employed. The intershaft bearing 49 is located to the left of the end of the inboard shaft 32. The outer race 5| of the bearing 49 is supported from the inboard shaft 32, through the inboard hub 36 and other elements hereinafter described, while the inner race 52 is mounted directly on the outboard shaft 3i.

The outboard hub, indicated generally by reference numeral 53, is secured to the outboard shaft 3| for rotation therewith as a unit by means of interengaging splines 54 and is centered with respect to said shaft by front and rear outboard cones 56 and 51, respectively, in substantially which in turn on its right-hand side abuts a spacing ring 59 which bears against the flange 41 on the outboard shaft.

A nut locking assembly, indicated generally by reference numeral 6| serves to lock the outboard shaft nut 58 to the outboard shaft 3|. The locking assembly 6| consists of a cup-shaped cap 62 fitted over the end of the outboard shaft 3| which has one or more rightwardly extending fingers such as 63 adapted to engage suitable notches or slots 64 in the periphery of the shaft adjacent the threaded portion thereof. The locking assembly 6|. Figs. 1, 5 and 20, also includes a pair of diametrically opposite telescoping pins 66 which are urged radially outward by a compression spring 61 whereby the ends enter radial holes 68 in the outboard shaft nut 58. The pins 66 engaging the shaft nut 58 prevent the same from turning relative to the lockthe same manner as the inboard hub 36 is mounted and centered on the inboard shaft 32. An outboard shaft nut 58 in threaded engagement with the outer end of the outboard shaft 3| cooping assembly 6 i, while the finger 63 engaging one of the slots 64 in the shaft 3| prevents the looking assembly from turning relative to the shaft. Thus, the shaft nut 58 is locked to the outboard shaft, and as the number of radial holes 68 in the shaft nut is diiferent from the number of slots 64 in the shaft, the nut 58 can be locked to the shaft 3| in practically any position to which it may be tightened thereon.

The inboard hub 36 has spaced around the periphery thereof substantially apart, as shown more clearly in Fig. 6. three substantially radially extending open-ended blade sockets 63. Each blade socket has mounted therein in a conventional manner well known in the art the shank of an.associated propeller blade 1|. The blade mounting elements include a so-called blade gear 12, Fig. 2, .threaded into the inside open shank end of the propeller blade and locked thereto by a pin 13. The radial thrust on each blade developed during rotation of the propeller is resisted by a thrust bearing indicated generally by reference numeral 14, consisting of a plurality of ball bearings arranged in a stack as shown. The inner ball race of the lower bearing, Fig. 2, engages a shoulder 76 on the blade gear 12, while the outer ball race of the uppermost bearing is engaged by the lower side of a nut ll. The nut Ti is threaded into the upper end of the blade socket 69 and is locked therein in a well-known manner by locking means which 7 may include keys 113 located in opposite radial slots in the upper surface of the blade socket and the nut, the keys being held in place by screws iii. The thrust bearing i4 permit the propeller blades 7| to rotate in their respective sockets 69 about the longitudinal axes thereof, whereby the pitch of the blades is changed. The manner in which this rotating movement of the blades is effected will be described hereinafter.

An insert 8| placed in the lower part of the blade gear 12 is faced with suitable resilient material 82, such as fiber or some similar substance. which bears against a suitable mating surface 83 of the propel er hub 36. When the nut 11 is tightened, the thrust produced thereby is transmitted' through the thrust bearing 14, the blade gear 12, the insert 8| and the resilient material 82 t0 the surface 83 of the hub 36, and in this manner the thrust hearing may be preloaded. Suitable circular packing rings or seals 84 and' 7 86 are associated with the nut 11. the blade shank II and the upper end of the blade socket 88 to prevent the escape of lubricant carried in the blade socket. The lubricant is provided in order to lubricate the thrust bearing I4 and other relatively moving elements carried by the hub. If the seals 84 and 88 were not provided, centrifugal force acting on the lubricant as the propeller rotates would force the same out of the blade sockets.

The outboard propeller hub 83 also has three blade sockets such as 81, Figs. 1, and 14, similar to the blade sockets 69 of the inboard hub 38, and each has mounted therein an associated propeller blade 88. The blades 88 are rotatably secured in their respective sockets 81 in substantially the same manner as the inboard propeller blades. The blade mounting elements of the outboard propeller include thrust bearings such as 89, blade nuts 9I and blade gears 92 fixed to and rotatable with their associated blades 88.

The forward or left-hand end, as shown in Figs. 1, 2 and 3, of the inboard hub 38 terminates in a flat radial surface 93 of relatively large diameter surrounding the shaft 32. Secured to the surface 93, by bolts such as 94, and located by dowel pins 95. is a so-called spur gear housing 98 and a so-called intershaft bearing housing 81. The spur gear housing 98 has a pair of circular flanges 98 which form a recess for and thus center the housing on the left-hand end of the hub. A circular seal 99 forms a tight fit between the hub and the housing. Opposite the circular surface 93 of the hub 36, the housing 98 has three leftwardly extending kidneyshaped projections I8I, Figs. 1, 3 and 6. The projections I8I are substantially 120 apart around the left-hand face of the housing 96, and each occupies substantially 50 of the circumference thereof. It is against these kidney-shaped projections I8I that the intershaft bearing housing 91 is clamped by the bolts 94. The latter housing 91 has axially extending circular flanges I82 which engage the inner and outer diameters of the kidney-shaped projections to insure correct alignment of the two members.

The bolts 94 employed to clamp the abovementioned housin members to the left-hand face or surface 93 of the inboard hub 36 are preferably hollow, as shown in the fragmentary section thereof in Fig. 2, with the heads 94a thereof to the left and the cooperating nuts 94!) at the right. The hollow bolts 94 provide a convenient means whereby electrical connections can be established between the hereinafter described slip rings, on the inboard end of the hub 36. and the pitchchange motor, generally designated by reference numeral I25, at the outboard end of said hub.

Secured to the outer part of the left-hand face of the spur gear housing 96 by suitable bolts, such as I88 and I83, Figs. 1, 3, 4, 6 and 23, and located by dowel pins such as I84, is the center section of the pitch-change motor housing, indicated generally by reference numeral I86. The pitchchange motor housing I86 is generally cylindrical with the axis thereof concentric with the propeller shafts, and has radially extending flanges I81 and I88 at its right and left-hand ends respectively. The outer rim of the right-hand flange I81 of the housing I86 abuts the spur gear housing 98, while the outer rim of the left-hand flange I88 has secured thereto by bolts such as I88, Fig. 23, and dowel pins such as III, a generally cylindrical, flanged housing member H2. The member II2, as best shown in Figs. 1 and 8,

serves as a housing unit for the left-hand end of the pitch-change motor and also as the righthand portion of the housing unit for the hereinafter-described inter-gearing mechanism. The housing member I I2 has a rightwardly extending cylindrical section H3 in the central portion thereof which terminates in an inwardly extending radial flange II4. To the flange H4 is secured by machine screws II6 the left-hand flanged end of the intershaft bearing housing 81. Thus, the intershaft bearing housing 91, the motor housing I88 and the housing member II2 form a toroidal-shaped cavity in which is mounted, in a manner hereinafter pointed out, the pitch-change motor of the power unit.

It is now also apparent, from the above described arrangement of housings, that because the housing 91 surrounds and supports the outer race SI of the intershaft bearing 49, and because the housing 91 is secured through the housing 96 to the inboard hub 36, which in turn is supported by the inboard shaft 32, said shaft 32 actually constitutes the primary support for said outer race 5| of said bearing 49, the inner race 52 of which is mounted directly on the outboard shaft 3I, the bearing 49 thus forming a true interbearing between said two shafts.

The cylindrical section I I3 of the housing member II2 carries on the outer periphery thereof the inner race II8 of the pitch-change motor armature bearing, indicated generally by reference numeral H9. The armature bearing H9 is a double row ball bearing, and the outer race I2I thereof is carried on the inside of the motor armature shell I22. An externally threaded nut I23 is threaded in the shell I22 and clamps the race I2I of the armature bearing against an inwardly extending radial flange I24 on the armature shell. The armature of the motor is indicated generally by reference numeral I26 and includes, in addition to the armature shell I22, the armature windings IN, the armature commutator segments I28 and the mounting ring I29 for said windings and segments; said ring being fixedly secured to the armature shell I22 as by a tight press fit therewith. Thus, the hollow armature I26 of the pitch-change motor is rotatabiy supported, through the housing members previously enumerated, by the inboard hub 36, and is, therefore, adapted to rotate about an axis concentric with that of the inboard propeller shaft 32.

The field coils of the pitch-change motor indicated by reference numeral I38 are wound about the poles I3I secured by screws I32 to the inside of a mounting ring I33 therefor, which, in turn, is secured to the motor housing I86 in a manner hereinafter pointed out. Motor brushes such as I34 engage the right-hand radial surfaces of the commutator segments I28 and are supported on the inner or lower ends, as shown in Fig. 3, of depending arms I35 of brush holders I36; the arms I35 being substantialy radial to the axis of rotation of the armature and propellers. The brush holders I36 are pivotally supported on pins I31 carried in the center section of the motor housing I86. The pins I31 are at right angles to the axis of the armature and propeller shafts, and permit the brush holders I36 to pivot in planes such as the plane of the section of Fig. 3. Each of the brush holders I36 has a cooperating compression spring I38 which tends to pivot the brush arms to hold the brushes I34 in engagement with the commutator segments I28. Suitable slots are formed in the motor housing I86 for mounting the brush holders I36 and for permitting the arms I35 thereof to extend through the wall of said housing.

The left-hand end of the armature shell I22, as shown in Fig. 3, flares outwardly, and formed integrally on the end thereof is a spur gear I39. The gear I39, which constitutes the armature or drive gear of the pitch-change motor, is concentric with the propeller shafts and has in engagement therewith three spur gears I4I, located approximately 120 apart around the periphery of the armature gear I39. Each of the gears I4 I, as shown in Fig. 4, is secured by rivets, such as I42, to the flange I43 of an associated hollow shaft I44; 9. construction which permits of the use of a non-metallic gear, if desired. There are, of course, three such hollow shafts I44, and hereinafter where the elements associated with but one of these are described, it is to be understood that each of the others has a similar set of associated elements. The hollow shafts I44, as shown in Fig. 4, are journaled parallel to the propeller shafts in ball bearings I46 to the left of the flanges I43 thereof, which in turn are supported in bushings I41 carried in the housing member II2. As shown in Figs. 1 and 4, the housing member II2 has cup-shaped sections I48 adjacent the periphery thereof which cooperate with similar sections I59, Figs. 1 and 4, on the forward flange of the motor housing I06 to form housings for the gears I4I.

Three relatively small inboard pitch-change speed reducers are driven directly by the hollow shafts I44, which also drive a single relatively large outboard pitch-change speed reducer through the medium of the hereinbefore mentioned inter-gearing mechanism. The inboard propeller speed reducers are indicated generally by reference numeral I49. Figs. 1 and 4 show in longitudinal section one such speed reducer, while Figs. 7, 8 and 9 show various transverse sections thereof, and Fig. 6 shows the forward end of all three and the relative positions thereof with respect to the propeller shafts. The spur gear housing 96 and the right-hand end of the motor housing I06 each have adjacent the outer rims thereof three similar sections I5I and I52, respectively, which form the main supporting and housing members for the speed reducers I49.

The right-hand end of each hollow shaft I44, as shown in Fig. 4, is supported by the left-hand end of a drive shaft I93 associated with the inboard speed reducer I49. The hollow shaft I44 is nonrotatably connected with the shaft I53 by means of a splined sleeve coupling I54, which engages splines on the adjacent ends of said shafts. The drive shaft I53 of each speed reducer I49 has keyed to its inboard or right-hand end, as shown in Figs. 1 and 4, a spur gear I55, which constitutes the sun gear of a planetary gear system. The sun gear I55. which is held on the shaft I53 by a nut I56 in threaded engagement therewith, meshes with two planet gears I51, which in turn mesh with an internal ring gear I58, as best shown in Fig. 9. The ring gear I58 is formed integral with the center frame member I59 of the housing of the speed reducer I49.

Referring again to the frame member I59 of the housing of the speed reducer I49, shown in detail in Figs. 1, 4, 7, 8 and 9, it will be noted that one of said members is fixed to the right-hand or open end of each section I52 of the housing 96 by bolts or screws such as I6I. In addition to holding the frame member I53 to the section I52, the

bolts or screws I6I hold a cap I62 against said member to close the inboard end of each housing section I52.

The planet gears I51, which engage opposite sides of the sun gear I55 and the ring gear I58, are rotatably mounted on shafts I63 by means of ball bearings I64. The shafts I63 are supported by a radially extending flange or spider I66 of a sleeve member indicated generally by reference numeral I61. The sleeve member I61 surrounds the right-hand portion of the drive shaft I53 and is rotatable independently thereof.

The sleeve member I61 is journalled in a ball bearing I68 which in turn is supported in the center section I69 of the frame member I59. The sleeve member I61 in turn supports, in the flared right-hand end thereof, a ball bearing I1 I, which supports the drive shaft I53 as shown.

The sleeve member I61 has formed integrally therewith adjacent its left-hand end a spur gear I12 which constitutes the sun gear of a second planetary gear system. As shown in Figs. 4 and 7, the sun gear I12 meshes with a set of planet gears I13, each of which has formed integrally and concentrically therewith another planet gear I14 of slightly smaller pitch diameter. Each pair of planet gears I13 and I14 is mounted on a short shaft I16 which is journalled in ball bearings such as I11. The bearings I11 are carried in a spider member I18 which is journalled concentrically with the drive shaft I53 on bushings I19 and I8I. The bushing I8I is supported on a centrally disposed leftwardly extending sleeve (portion I82 of the frame member I59. The bushing I19 is supported on a centrally disposed section I83 of a sleeve member I84, which surrounds but is not in contact with the shaft I53. As shown, the sleeve I83 supports a bushing I86 which serves as a bearing for the left-hand end of the sleeve member I 6.1.

At its right-hand end, the sleeve I84 has formed integrally therewith an internal ring gear I88, which meshes with the planet gears I13. Another internal ring gear I89 formed integrally with the housing frame member I59 meshes with the planet gears I14.

The sleeve member I84 has formed adjacent the left-hand end thereof external splines I9I which engage internal splines I92 on the hub I93 of a pinion I94. The hub I93 is journalled in two ball bearings I96 which are supported in the sections I5i and I52 of the housing members 96 and I06. The hub I93 supports in its lefthand end a ball bearing I91 in which is journalled the left-hand end portion of the drive shaft I53. As best shown in Figs. 1, 3, 4 and 6, the pinion I94 of each of the three speed reducer units I49 meshes with a large gear I98 mounted concentrically with the inboard propeller shaft 32. The gear I98 is rotatable with respect to said shaft and has a leftwardly extending hub portion I99, Fig. 3, journalled in a bushing 20I supported by the innermost flange I02 of the housing member 91. The gear I98 occupies the space formed by the spur gear housing 96, the intershaft bearing housing 91 and the flange I0] of the motor housing I06.

As shown most clearly in Fig. 6, the gear I98 has three kidney-shaped holes or slots 203 in the web portion thereof through which extend the three kidney-shaped projections IOI of the housing 98. The slots 203 are considerably longer than the projections IM and, therefore, appreciable rotation of the gear I98 is permitd. T e bore of the gear I98 has splines 204 11 cut therein. and these splines engage cooperating external splines on the left end, Figs. 1, 3 and 6, of the hub 206 of a bevel gear 201 that meshes with all of the blade gears 12, each of which comprises a bevel gear segment 209, Figs. 1, 2, 3 and 6. adapted to mate with said ear 261.

A spacing ring 208 surrounding the hub 206 rotatably supports the gear 201 as shown and also positions the same with respect to the bevel gear segments 209 by means of shims 208a, Fig. 3,. interposed between said ring and said gear 201.

The amount, which may be varied at will, that the spur gear I98 and the bevel gear 201 splined thereto may rotate in the illustrated design, as determined by the relative lengths of the kidney-shaped projections III! and the similarly shaped slots 203 in the web of the gear I93, is suflicient to produce the maximum desired pitch change of the blades. With the arrangement shown, the blades may be rotated from a position of about 15 positive pitch to a full feathering or 90 pitch position.

The previously mentioned differential gearing or so-called inter-gearing, which constitutes an important feature of the present invention, and which is utilized, among other purposes, for coordinating the action of the inboard and outboard pitch-changing units, is hereinafter generally referred to and indicated in the drawings by reference numeral 2I I. The complete intergearing mechanism is positioned as shown in Figs. 1 and 3 to the left of the pitch-change motor which includes the armature I26 and its hereinbefore described associated elements. For reasons which will presently be explained, it is desirable that the driving connections between the inter-gearing and each of the three inboard pitch-change mechanisms I49, Figs. 1 and 3, be of a flexible or resilient. nature. Accordingly, small-diameter, relatively long and suitably supported flexible shafts 2I2, Fig. 4, which are termed torsion rods. are employed for this purpose.

One of these torsion rods 2I2 is associated with each of the pitch-change units I49 and is mounted within the hollow drive shaft I connected therewith. Each torsion rod M2 is pinned by a shear pin such as M3 to the right-hand end of its associated hollow shaft I, and to the left-hand end of each rod is secured by means of a pin 2 a pinion 2I6. A longitudinally split sleeve 2Il of suitable non-metallic material snugly surrounds each rod 2|2 intermediate the enlarged ends thereof, substantially filling the annular space between the rod and the hollow shaft I. This construction obviously prevents transverse fiexure of the torsion rod due to the action of centrifugal force thereon during rotation of the propeller or other causes.

The three pinions 2I6 on the left-hand ends of the torsion rods 2I2, as best shown in Figs. 4 and 11, mesh with a large spur gear 2I8 formed on the outer periphery of a circular member 2I9 mounted concentrically with the inboard propeller hub 36. As the three pinions 2I6, which are intended to cooperate with each other to drive the gear 2I8, are all driven by a common gear, namely, the motor armature gear I39, through the medium of the gears HI and shafts I44 and 2I2, it is obvious that the manufacturing tolerances of all of said parts and associated members would of necessity be extremely limited if the \three separate driving connections between the gears I33 and 2I8 were rigid. Accordingly, the flexible torsion rods 2I2 are provided in these three driving connections, so that if the teeth on one or more of the pinions 2I6 fail to lineup properly for engagement with the teeth of the gear 2| 3, such misalignment may be readily compensated for by the slight rotation of said pinion or pinions permitted by the flexibility of said torsion rods or shafts 2I2.

The shear pins 2I3 connecting the right-hand ends of the hollow shafts I with the torsion rods 2I2 are provided to prevent any possible damage to the inter-gearing mechanism or the elements operatively connected therewith should they become over-loaded due to extraordinary conditions.

The gear 2| 8 which is integral with the circular member 2I3, Figs. 3, 4, 11 and 12, is directly and rotatably supported on a bearin comprising a circular row of balls 22I which are supported by a race 222. The race 222 is secured by rivets 223 to a flanged circular forging 224. The forging 224 and an inter-gearing housing member 226 are secured by the bolts I09, Fig. 23, to the left-hand end of the motor housing member I I2.

The race 222 also serves as the outer race of a second ball bearing 22'! which rotatably supports an annular member 228, hereinafter referred to as the inter-gearin spider. The inner periphery of the spider 228 is formed to serve as the outer race of a third ball bearing 229, the inner race 2:, of which supports the sleeve portion 232 of a flanged inter-gearing housing member 233. The sleeve 232 surrounds the right-hand sleeve portion of the outboard hub 53 but is out of engagement therewith to the extent of about 1 6 inch radially as shown in the accompanying draw ings. A nut 234 which is threaded on the righthand end of the sleeve 232 clamps thereon an oil slinger disc 235, a gear 236, the ball race 23I, a spacer ring 231 and a bearing bushing 238, in the order named. The gear 236 which surrounds and is mounted on the sleeve portion 232 of the housing member 233 is also secured thereto by means of a key 233.

The housing member 233 is arranged to rotate with the outboard propeller hub in a manner hereinafter described, but is positively carried by and rotatably mounted on the inboard propeller hub through the medium of the two ball bearings 229 and 221 which are supported by the hub 36 through the housing member I I2, as previously explained herein.

As stated in the first part of this specification. the inboard and outboard pitch-changing units embodied in the present invention are interconnected by differential gearing, above referred to as the inter-gearing mechanism 2I I, which may be of either the spur-gear or bevel-gear type. If of the spur-gear type, it will be understood that the spur-gears maybe toothed either externally or internally. In the preferred form of the invention, this differential gearing is of the spurgear type, as is best shown in Figs. 3 and 11, and comprises a double planetary gear system consisting of two sun gears, two sets of planet gears and two internal ring gears meshing respectively with said two sets of planet gears. The previously mentioned gear 236 is one of the sun gears of said system and is concentrically mounted on the sleeve 232 to which it is non-rotatably secured in the manner described. The other sun gear 248, of said system, is also concentrically mounted on the sleeve 232, but is free to rotate relatively thereto on the bearing 238. As shown,

both sun gears have the same pitch diameter. The sun gear 236 meshes with one set of planet gears 243 rotatably supported by ball bearings 242 carried on stub shafts 241 secured, as shown, to the spider 228. The sun gear 248 meshes with another set of planet gears 244, similarly but independently mounted on the opposite side of said spider. All planet gears 243 and 244 have the same pitch diameter. The planet gears 243 mesh with an internal ring gear 246, which is formed integral with the member 2l9 and gear 2l8, while the planet gears 244 mesh with an internal ring gear 241, which is formed integral with the forging 224 secured to the housing member H2.

The sun gear 248 is formed integral with a sleeve member 249 to the left thereof, Figs. 3 and 4, and around the left end of said sleeve is formed a gear 25! also integral therewith and generally similar to the gear 248. The gear 25! meshes with three symmetrically disposed gears 259, Figs. 3, 4 and 14. Each gear 259 is secured by rivets 258 to a flanged hub 251 which is secured to a shaft 254 by a key 255 and a nut 256; a construction which permits of the use of a non-metallic gear, if desired. Each shaft 254 is supported by ball bearings 253 carried by a suitable extension 252 of the housing member 233, which is rotatably mounted on a bearing supported indirectly but positively by the inboard propeller hub, as previously explained herein.

The gears 259 are located a slight distance to the left of the radial flange section 26l of the housing member 226 which has on the inner diameter thereof labyrinth sections 262. The labyrinth sections 262 in cooperation with a similar section 268 on the sleeve member 249 are provided to prevent or minimize the escape of oil or other lubricant from the inter-gearing mechanism 2| I.

Non-rotatably secured to the outboard hub 53 by suitable means such as bolts or cap screws is a flanged casting 264, Figs. 4 and 14, which has in the outer section thereof three open-end cylindrical extensions 266 spaced 120 apart and normally respectively concentric with the shafts 254 which pass freely therethrough. A ball bearing 268 is mounted on an extension 268a of the housin member 233 loosely surrounding each shaft 254. Vulcanized or otherwise suitably secured to the inner surface of each cylindrical extension 266 of the casting 264 is a buffer ring 261 of rubber or other pliant material adapted to engage the outer race of the ball bearing 268 when the clearance, which is plainly indicated in Fig. 4, between said ring and said race is taken up by relative rotary movement between the member 233 and the casting 264. Obviously, by this arrangement .the inter-gearing housin member 233, which is rotatably supported from the inboard hub 36 in the manner hereinbefore described, is constrained to rotate with the outboard hub 53 when the propellers are in operation. The difference between the inside diameter of the buffer ring 261 and the outside diameter of the outer race of the ball bearing 268 is comparatively small so that only a negligible amount of relative rotation between the casting 264 and the housing member 233 is permitted. This difference in diameters or clearance is provided to prevent interference with the operation of the pitch-change gearing when relative flexure occurs between the inboard and outboard propeller shafts 32 and 3| respectively.

The left-hand end of each shaft 254, Fig. 4, has keyed or splined thereto a metal sleeve 265, to the outside of which is vulcanized a rubber or other pliant material bushing 289. A second metal sleeve 210 is vulcanized to the outside of each bushing 269, and the left-hand end of each sleeve 218 is provided with teeth or projections adapted to engage axial slots or keyways 215, Figs. 1'5 and 16, adjacent the right-hand end of an associated metal tube 21l. The tubes 2" have enlarged ends, and each metal sleeve 218 with the attached rubber bushing 269 is secured to its associated tube 211 by means of a nut 212 in threaded engagement with the right-hand end thereof. Into the left-hand end of each metal tube 211 is tightly pressed a sleeve 213a, Fig. 5, vulcanized to the outside of an associated rubber or other pliant material bushing 213. Each bushing 213 is vulcanized to an internal sleeve 214a, which is secured by keys or splines to an associated drive shaft 214. By means of the construction above described, it is obvious that there is provided a flexible driving connection between the shafts 254 and 214, Figs. 4 and 5, that permits of both axial misalignment and slight torsional movement between said shafts, which may be rendered necessary by relative fiexure between the inboard and outboard propeller shafts or by other causes, such as manufacturing inaccuracies.

The shafts 214, of which there are three, are .iournalled adjacent the center sections thereof in ball bearings 216 and 211. The ball bearings 216, Fig. 5, are carried by the right-hand portion of a housing 218 that supports the outboard speed reducer which is indicated generally by reference numeral 219. The housing 218 is secured by suitable means such as bolts or screws to the front end of the outboard hub 53. The ball bearings 211 are supported by a disc forging 28l suitably secured, together with a cover casting 282 by bolts such as 288 to the forward or left-hand end, as shown in Figs. 1 and 5, of the housing 218. Located around each shaft 214 and between the ball bearings 216 and 211 is a sleeve 283 and a compression spring 284. As is evident from the drawings, this sleeve and spring serve as a flexible spacer to hold the bearings 216 and 211 in place longitudinally in their respective supports. The inner races of said bearings, the sleeve 283 and the spring 284 all flt slidably on the shaft 214 which, therefore, is free to move longitudinally with respect to the housing 218. This construction prevents binding of the parts concerned if the propeller hubs move out of mutual alignment, and it also eliminates the necessity for close manufacturing tolerances.

The shafts 214 constitute the drive shafts for the outboard speed reducer 219, Figs. 1, 5, 1'1, 18 and 19, and each has pinned to the forward end thereoef a pinion 286 that meshes with a relatively large spur gear 281 journaled concentrically, as shown, with the outboard propeller shaft 3|. Formed integral with the gear 281 is a pinion 29| which constitutes the sun gear of a planetary system. The sun gear 291, as best shown in Fig. 18, meshes with a set of planet gears 292, which in turn mesh with an internal ring gear 293 formed integral with the disc forging 28! which, as previously stated, is bolted tothe housing 218. Each of the planet gears 292 is mounted on a shaft 294 journaled on a pair of ball bearings 296, carried by a casting or spider 291, which is concentrically journalled, as shown, with the gear 281 for free rotation relative. thereto on bearings 299 and 38!. The spider 291 also carries a central bearing "9 which rotatably supports an extension 290 of the hub of the integral gears 281 and 29I.

Formed integral with each of the planet gears 232 is a secondary planet gear 298, Figs. and 19, of slightly smaller pitch diameter. These secondary planet gears mesh with a relatively large internal ring gear 303 having a hollow hub 304 rotatably supported by bearings 309 and 3 II carried by the housing 218. The inner race of the bearing 309 is not mounted directly on the .hub 304 but on the hub of a bevel gear 308 that is fitted thereto and drivably connected therewith by splines 306 and 301, as best shown in Fig. 5, where it will be noted that the gear 303 has a central extension 302 which serves to support the previously mentioned bearing 30I. The bevel gear 308 meshes with all of the blade gear segments 3I0 formed integral with the several blade gears 92 attached to the blades 88 of the outboard propeller, as shown in Figs. 1. 5 and 14.

Referring to Fig. 5, it will be noted that the geear 303 is shown as having a lug 3I2 extending radially therefrom. There are three such lugs located substantially 120 apart and, extending into the path of movement of these lugs as the gear 303 rotates, are three similar lugs 3I3 formed integral with the disc forging 28I which, as previously explained, is bolted to the housing 218. It is evident from an inspection of Fig. 5 that these two sets of lugs cooperate to limit the amount of rotation of the gear 303, so asto eliminate the possibility of changing the pitch of the propeller blades beyond safe limits for normal operation.

Fixed to the forward face of the inter-gearing spider 223, Figs. 3 and 13, by screws 3I5 are diametrically opposite brackets 3I4 and 3I6 which have secured thereto associated oil scooping tubes 3" and 3I8, respectively. The outer ends or the tubes 3H and 3I8 terminate adjacent the inside diameter of the housing member 228 and are curved as shown so that oil or other liquid lubricant in said housing will be scooped up by the tubes when the propellers are rotating and conveyed to various parts of the inter-gearing mechanism.

A magnetic brake mechanism is employed in the preferred embodiment of the invention to stop and hold the armature of the pitch-change motor against rotation relative to its field when the circuit thereto is opened after any desired amount of change in the pitch of the propeller blades has been effected. The electric circuit to the magnetic brake mechanism which is spring applied is preferably included in the circuit of the pitch-change motor and is so arranged that the brake is released when the motor is energized.

The brake mechanism includes three electromagnetic units, one of which is shown in Figs. 1, 3 and 4, wherein it is indicated generally by reference numeral 3I3. The magnetic coils 322 are wound on a flanged core 323 which surrounds the hollow shafts I44 but is out of contact therewith and is secured to the flange section I08 of the motor housing I05 by a plurality of screws such as 32 I.

Interposed between the magnetic units 3I9 and the flanges I43 of the shafts I44 is a flexible brake plate 324, generally triangular in shape and having a central bore adapted to clear the motor field coils I30, Figs. 3, 4 and 10. This plate 324, which is made of iron or other magnetic material, is secured at three central points by screws such as 326 to the open left-hand end of the motor housing I08, and has substantially circular sections 328 at the corners thereof to which are attached by means of rivets, such as 323, discshaped sections 33I of suitable brake lining material. Each of the brake discs 33I is located on the brake plate 324 in such a position that it surrounds one of the hollow shafts I44 and is adapted to cooperate with the metal flange I43 thereof to exert a, braking action thereon.

During an unenergized condition of the magnetic units 3I9, compression springs 332, only one of which is partly shown in Fig. 4, are adapted to flex the brake plate 324 and press the corners thereof carrying the brake discs 33I against the right-hand faces of the three shaft flanges I43 and thereby prevent the same from rotating. The left end of each compression spring 332 is mounted in a recess such as 333 formed in the brake plate 324 and the opposite end of each spring is located in a suitable bore formed in the outer left-hand end of the motor housing I08. When the circuit of the pitch-change motor I25 is completed, the brake coils 322 are energized, since they are included in the motor circuit, and the magnetic action thereof moves the flexible plate 324 to the right, as shown in Fig. 4, against the action of the compression springs 332, thus drawing the brake discs 33I out of engagement with the flanges I43 of the hollow shafts I44, which are then free to rotate. When the motor circuit is opened, the coils 322 are deenergized and the springs 332 are then effective to reapply the brakes.

Suitably secured to the inboard or right-hand side of the inboard hub 36 is a slip ring assembly, indicated generally by reference numeral 334, Figs. 2 and 21. This assembly consists of a plurality of slip rings 336 of suitable electrical conducting material separated by insulating discs 33! mounted on an insulating sleeve 338. The slip rings 336 are electricall connected through suitable circuits to the proper terminals of the magnetic brakes and the pitch-change motor in a manner well-known in the art, and, therefore, a detailed description thereof will not be included herein. Limit switches, also well-known in the art, may be employed in the pitch-change motor circuit to open it when the pitch of the propeller blades has been altered to a desired limiting value in either direction. Such switches prevent damage to the pitch-changing mechanism and are automatic in operation.

A slip-ring housing 339 is bolted to the front end of the associated engine (not shown) by bolts extending through holes such as 3, Fig. 21. The housing 339 has an opening in the right-hand side thereof, as shown in Fig. 21. and to this opening is clamped by means of trunk type clamps 342 a brush assembly 343, Figs. 21 and 22. The brush assembly 343 includes brushes 344 which under the influence of springs 345 are adapted to engage the slip rings 336 and establish electrical connections between the slip rings and the conductors of a cable 346. The cable 346 is connected to the brush holder assembly through a connector 341. The connector 341 and the clamps 342 enable the brush assembly 343 to be completely and quickly removed from the propeller unit and cable 346.

It will be obvious to those familiar with devices such as those disclosed herein that it is essential that various of the relatively moving parts of the propeller be thoroughly lubricated. In the disclosed embodiment of the invention, for example, the planet gears 243 and 244 of the differential inter-gearing mechanism 2 are 

